PATCH: Make _errno/errno available in GLIBC_2_0.

[Roland McGrath]

> I am not against that. But it should be consistent between linuxthreads
> and nptl.

Why?  It's possible, easy, and most importantly *already done* for
linuxthreads to provide ABI compatibility with glibc-2.0 programs.  
Why break it?

> FWIW, the "ancient" binary is portmap from RHAS 2.1.

And the glibc for that system supports it, but we are not still maintaining
that version as part of glibc development and it's "ancient" in many other
regards as well.